DE102021208772B4 - Half-bridge for an inverter for operating an electric vehicle drive, power module comprising several half-bridges, inverter, method for producing an inverter - Google Patents

Abstract

Half-bridge (10A, 10B) for an inverter for supplying current to an electric drive in an electric vehicle and/or a hybrid vehicle, comprising:- a plurality of semiconductor switching elements (12) which form a high side and a low side connected in series with the high side, wherein during operation of the half-bridge a higher electrical potential is present at the high side and a lower electrical potential is present at the low side,- a substrate, on the first side (144) of which the semiconductor switching elements are mounted and on the second side opposite the first side of which a heat sink of the inverter can be connected,wherein the inverter has a circuit board (16) on which a plurality of electronic components for switching the semiconductor switching elements (12) are connected to them via a plurality of current and/or signal lines,wherein a conductor body (18) is fastened between the circuit board (16) and the substrate, so that the conductor body (18) is received by the circuit board (16) in a form-fitting, force-fitting and/or material-fitting manner in order to form an electrical line between a current contact (124) of the semiconductor switching elements (12) and a metallization (14) on the first side (144) of the substrate, wherein the substrate has a second opening (142) in which the conductor body (18) is received at its substrate-side end in a constructed state of the half-bridge (10A).

Description

TECHNICAL AREA

The present invention relates to the field of electromobility, in particular to inverters for operating an electric drive for a vehicle.

TECHNICAL BACKGROUND

Power modules are increasingly being used in motor vehicles. They are used, for example, in DC/AC inverters, which are used to supply electrical machines such as electric motors with a multi-phase alternating current. Such power modules are based on semiconductor switching elements, in particular transistors such as IGBTs, MOSFETs and HEMTs. By specifically switching the semiconductor switching elements, a direct current generated from a DC energy source, such as a battery, is converted into a multi-phase alternating current. The power module usually comprises several so-called half-bridges, each of which has a high side and a low side. Each high side or low side comprises one or more semiconductor switching elements. In order to generate a three-phase alternating current at the output of the inverter, three half bridges are used in the inverter, with each half bridge being permanently assigned to one of the three phase currents.

The WO 2021/ 152 021 A1 introduces a compact, configurable power semiconductor module that achieves low stray inductance and high power density by arranging semiconductor chips on a semiconductor board and an adapter board with vertical conductive posts. The module enables flexible topologies and provides separate connections for power and control electrodes of each chip, enabling a variety of circuit arrangements and improved efficiency. In addition, the structure results in symmetrical heat dissipation and increased reliability of the module.

EN 10 2015 224 431 A1 describes a power semiconductor module that has difficulties with high inductance due to its size and long current paths. The invention addresses this problem by means of a semiconductor device that includes several semiconductor units, each of which forms a three-level inverter circuit. These units are electrically connected in parallel and consist of a multilayer substrate, semiconductor elements and wiring elements. The configuration enables the inductance of the wiring to be reduced while simultaneously increasing the current carrying capacity.

The power module according to DE 196 45 636 C1 is characterized by a compact integration of several functional units in a common housing. The technical features include: semiconductor components on a substrate that is soldered directly onto an efficient cooler, a separate control unit on a carrier body with optional EMC shielding, and the possibility of integrating additional functional units. The advantages include improved heat dissipation, increased reliability and service life, and minimized circuitry effort through optimized cable lengths.

To enable fast and power-efficient switching of the semiconductor switching elements, so-called wide band gap (WBG) semiconductors (i.e. semiconductors with large band gaps) such as silicon carbide (SiC) or gallium nitride (GaN) are used. Such semiconductor switching elements are applied to a metal layer that is connected to a heat sink via an insulation layer in order to cool the semiconductor switching elements, which carry high currents and generate heat when the inverter is operating. For example, the metal layer can be part of a multilayer substrate, such as a direct-bonded copper (DBC) substrate.

In the case of semiconductor switching elements designed as transistors (such as IGBTs), it is important for such WBG semiconductors to electrically connect the source electrode of the transistor and the metal layer on which the semiconductor switching elements are applied so that they always have the same electrical potential. However, in the case of inverters known from the state of the art, it is complex due to their design to create this electrical connection between the source electrode and the metal layer.

The invention is therefore based on the object of providing a half-bridge in which the disadvantages described above are at least partially overcome.

This object is achieved by a half-bridge, a power module, an inverter and a method according to the independent claims.

The invention relates to an inverter (DC/AC inverter) for operating or supplying current to an electric drive of an electric vehicle and/or a hybrid vehicle. The inverter is used to generate a multiphase alternating current comprising several (for example three) phase currents from a direct current generated by means of a DC voltage of an energy source, such as a battery.

The inverter comprises a power module which has a plurality of semiconductor switching elements. The semiconductor switching elements form a plurality of, for example three, half-bridges, each of which is assigned to a phase current of the multi-phase alternating current. Each half-bridge comprises a high side and a low side. The high side comprises one or more semiconductor switching elements connected in parallel to one another, to which a comparatively positive or higher electrical potential is applied when the half-bridge is operating. The low side comprises one or more semiconductor switching elements connected in parallel to one another, to which a comparatively negative or lower electrical potential is applied when the half-bridge is operating. The high side and the low side are connected in series with one another.

It is preferably provided that the semiconductor switching elements are designed as bipolar transistors with insulated gate electrodes (IGBTs) and/or as metal oxide semiconductor field effect transistors (MOSFETs). A so-called wide bandgap semiconductor (WBS) such as silicon carbide (SiC) or gallium nitride (GaN) is preferably used as the semiconductor material underlying the semiconductor switching elements. These types of semiconductor switching elements are comparatively well suited for low-loss and fast switching even at high currents.

The substrate can be designed, for example, as a DBC (Direct Bonded Copper) substrate, as an AMB (Active Metal Brazing) substrate or as an IM (Insulated Metal) substrate. The semiconductor switching elements are arranged on a first side of the substrate. A heat sink can be connected to a second side opposite the first side in order to dissipate the heat that is generated during operation of the semiconductor switching elements. The substrate is preferably rectangular, in particular as a flat, disk-like rectangle, with two opposite side edges. If necessary, the substrate can also be square. If the substrate is designed as a DBC substrate, the substrate comprises a first and a second metal layer and an insulation layer arranged between them, with the semiconductor switching elements being attached to the first metal layer. The heat sink is preferably connected to the second metal layer opposite the first metal layer.

For the purpose of switching the semiconductor switching elements, control electronics comprising several electronic components that are placed on a circuit board are used. The circuit board is integrated in the inverter so that these are connected to the semiconductor switching elements via power and/or signal lines. According to the invention, a conductor body is attached between the circuit board and the substrate so that an electrical line is provided between a power contact of the semiconductor switching elements and a metallization on the first side of the substrate.

In this way, the electrical connection between the current contact of the semiconductor switching elements and the metallization of the substrate can be created particularly easily, and is particularly reliable due to the positive, non-positive and/or material connection. The current contact of the semiconductor switching elements is therefore always at the same electrical potential as the metallization of the substrate, namely ground. This promotes a lower inductance in the inverter, which is advantageous in terms of reducing or even eliminating voltage jumps when the semiconductor switching elements are switched quickly.

Advantageous embodiments and further developments are specified in the subclaims.

According to one embodiment, a metallization is provided on an underside of the circuit board facing the semiconductor switching elements, which connects the current contact of the semiconductor switching elements and the conductor body in an electrically conductive manner. As a result, the current contact with the metallization and the conductor body is on the same electrical signal, which reduces the inductance of the inverter.

According to a further embodiment, the circuit board has a first opening in which the conductor body is received at its circuit board-side end in a constructed state of the half-bridge. This enables a simple and at the same time stable electrical and mechanical connection of the conductor body to the circuit board.

According to a further embodiment, the first opening is a through-opening through which the conductor body is guided in a direction pointing towards the substrate. The conductor body is connected to the circuit board over the entire thickness of the latter. The stability of the electrical and mechanical connection of the conductor body to the circuit board is thereby increased.

According to a further embodiment, the conductor body is connected to an inner wall of the first opening by means of frictional forces and/or a welding process, for example a laser welding process. This measure additionally increases the stability of the electrical and mechanical connection of the conductor body to the circuit board.

According to a further embodiment, the conductor body is attached to the substrate at its substrate-side end by means of a soldering process and/or a welding process. This measure ensures increased stability of the electrical and mechanical connection of the conductor body to the metallization of the substrate.

According to the invention, the substrate has a second opening in which the conductor body is accommodated at its substrate-side end in a constructed state of the half-bridge. This measure additionally increases the stability of the electrical and mechanical connection of the conductor body to the metallization of the substrate.

According to one embodiment, the method according to the invention for producing an inverter further comprises providing a first opening in the circuit board, connecting the semiconductor switching elements attached to the substrate to the underside of the circuit board so that the current contact of the semiconductor switching elements is electrically conductively connected to an underside metallization of the circuit board, and attaching the conductor body to the circuit board so that the conductor body is received in the first opening in an assembled state of the inverter and electrically conductively connects the underside metallization of the circuit board to the metallization on the first side of the substrate.

According to one embodiment, the method according to the invention further comprises providing a second opening in the substrate before the semiconductor switching elements mounted on the substrate are connected to the underside of the circuit board, and passing the conductor body through the first opening, which is designed as a through-opening, and into the second opening.

According to a further embodiment, the method further comprises fastening the conductor body on the first side of the substrate before the semiconductor switching elements mounted on the substrate are connected to the underside of the circuit board, and connecting the conductor body to an inner wall of the first opening by means of a welding method, in particular a laser welding method.

• 1 eine schematische Darstellung einer Halbbrücke gemäß einer Ausführungsform in einer Seitenansicht;
• 2 eine schematische Darstellung eines Verfahrensschrittes zum Herstellen der Halbbrücke in 1;
• 3 eine schematische Darstellung eines weiteren Verfahrensschrittes zum Herstellen der Halbbrücke in 1;
• 4 eine schematische Darstellung eines weiteren Verfahrensschrittes zum Herstellen der Halbbrücke in 1;
• 5 eine schematische Darstellung eines weiteren Verfahrensschrittes zum Herstellen der Halbbrücke in 1;
• 6 eine schematische Darstellung einer Halbbrücke gemäß einer weiteren Ausführungsform in einer Seitenansicht;
• 7 eine schematische Darstellung eines Verfahrensschrittes zum Herstellen der Halbbrücke in 6;
• 8 eine schematische Darstellung eines weiteren Verfahrensschrittes zum Herstellen der Halbbrücke in 6;
• 9 eine schematische Darstellung eines weiteren Verfahrensschrittes zum Herstellen der Halbbrücke in 6.

Embodiments will now be described by way of example and with reference to the accompanying drawings, in which:

• 1 a schematic representation of a half-bridge according to an embodiment in a side view;
• 2 a schematic representation of a process step for producing the half bridge in 1 ;
• 3 a schematic representation of a further process step for producing the half bridge in 1 ;
• 4 a schematic representation of a further process step for producing the half bridge in 1 ;
• 5 a schematic representation of a further process step for producing the half bridge in 1 ;
• 6 a schematic representation of a half-bridge according to another embodiment in a side view;
• 7 a schematic representation of a process step for producing the half bridge in 6 ;
• 8th a schematic representation of a further process step for producing the half bridge in 6 ;
• 9 a schematic representation of a further process step for producing the half bridge in 6 .

In the figures, identical reference symbols refer to identical or functionally similar reference parts. The relevant reference parts are marked in the individual figures.

1 shows a schematic representation of a half-bridge 10A according to an embodiment in a side view. The half-bridge 10A is used in an inverter for powering an electric drive in an electric vehicle and/or a hybrid vehicle. Several semiconductor switching elements are installed in the inverter, which are several, for example three, half-bridges 10A, each of which is assigned to a phase current of a multi-phase alternating current. Each half-bridge 10A comprises a high side and a low side. The high side comprises one or more semiconductor switching elements connected in parallel to one another, to which a comparatively positive or higher electrical potential is applied when the inverter is operating. The low side comprises one or more semiconductor switching elements connected in parallel to one another, to which a comparatively negative or lower electrical potential is applied when the inverter is operating. The high side and the low side are connected in series with one another. By means of targeted switching, a direct current (DC current) provided by a battery, which is fed into the inverter on the input side, is converted into the multi-phase alternating current (AC current) at the output of the inverter. The phase currents of the output current are used to power the electric drive of the electric vehicle or hybrid vehicle.

In 1 purely schematically, only one semiconductor switching element 12 is shown, which can be designed as a bipolar transistor with an insulated gate electrode (IGBT) and/or as a metal oxide semiconductor field effect transistor (MOSFET). A so-called wide bandgap semiconductor (WBS) such as silicon carbide (SiC) or gallium nitride (GaN) is preferably used as the semiconductor material underlying the semiconductor switching element 12. The semiconductor switching element 12 is attached to a first side 144 of a substrate. The substrate preferably has a multilayer structure with an upper metallization 14. A lower metallization can be present in the substrate, which is electrically separated from the upper metallization by insulation also located in the substrate and to which a heat sink can be connected for dissipating heat generated in the semiconductor switching elements 12 (not shown).

A circuit board 16 is provided in the inverter, which is equipped with several electronic components. These electronic components are connected to the semiconductor switching elements 12 via signal and/or power lines in order to transmit current and control signals to them. Sensors for detecting current, voltage, temperature and/or short circuits of the half bridges 10A can also be integrated on the circuit board.

As in 1 As shown, a conductor body 18 is arranged in the half-bridge 10A in such a way that it is fastened between the circuit board 16 and the substrate. In particular, the conductor body 18 is in electrical connection with a metallization 164, which is attached to an underside 161 of the circuit board facing the substrate and is electrically conductively connected to a current contact 124 of the semiconductor switching element 12, and the upper metallization 14 of the substrate. The current contact 124 is preferably a source contact, wherein the semiconductor switching element 12 is designed as a transistor.

In 2 to 5 A process for producing the 1 shown half bridge 10A is shown schematically. First, as in 2 shown, the semiconductor switching element 12 is connected to the first side 144 of the substrate, for example by means of welding, for example laser welding, or soldering. In addition, an opening 142 is formed in the upper metallization 14 of the substrate. The opening 142 can extend over the entire or partial thickness of the upper metallization 14 of the substrate. However, the opening 142 already ends above the above-mentioned lower metallization of the substrate, so that the electrical insulation between the upper and lower metallization is ensured. In the lower drawing of 2 In addition to the current contact 142 designed as a source contact, a drain contact 122 and a gate contact 126 of the semiconductor switching element 12 are shown purely schematically in a plan view.

In one after the other 2 shown process step, which is carried out in 3 , an opening 168 is provided in the circuit board 16. The opening 168 is preferably a through-hole as shown here.

Subsequently, in a further process step, as in 4 shown, the circuit board 16 is connected to the semiconductor switching element 12, so that a metallization 166 of the circuit board is electrically connected to the drain contact 122, wherein the metallization 164 is also electrically conductively connected to the source contact 124. Thereafter, the conductor body 18, as in 5 shown, from top to bottom (see arrow), first through the through-opening 168 of the circuit board 16 and then into the opening 142 of the upper metallization 14 of the substrate. The diameter of the two openings 142, 168 is selected such that the conductor body 18 is held and secured by frictional forces on the inner walls of the openings 142, 168 after insertion. In addition, the conductor body 18 is electrically connected to the metallizations 164, 14. In this way, the source contact with the metallization 164 and, via the conductor body 18, also with the upper metallization 14 of the substrate is at the same potential, preferably at ground/earth potential.

6 shows a schematic representation of a half-bridge 10B according to a further embodiment in a side view. Here too, the conductor body 18 is in electrical connection with the metallizations 164, 14. The source contact is at the same potential as the metallization 164 and, via the conductor body 18, also with the upper metallization 14 of the substrate, preferably at ground/earth potential.

In the 6 The embodiment shown differs from that in 1 shown embodiment in that the upper metallization 14 has no opening or through-opening. Here, the conductor body 18 is not received in an opening in the upper metallization 14 of the substrate on the substrate side, but is fixed on the first side 144 by means of a connection technology, such as welding, for example laser welding. In addition, the conductor body 18 is received in the opening 168 on the circuit board side and is additionally connected to the inner wall of the opening 168 by means of welding or laser welding.

In 7 to 9 A process for producing the 6 shown half bridge 10B is shown schematically. First, as shown in 7 shown, the semiconductor switching element 12 is connected to the first side 144 of the substrate, for example by means of welding, for example laser welding, or soldering. In addition, the conductor body 18 is attached to the first side 144, for example by means of welding, for example laser welding, or soldering. The lower drawing of the 7 shows the structure in a top view. In a model according to 7 shown process step, which is carried out in 8th As shown, an opening 168 is provided in the circuit board 16. The opening 168 is, as shown here, preferably a through-hole. Subsequently, in a further process step, as shown in 9 shown, the circuit board 16 is connected to the substrate from above in such a way that the conductor body 18 already attached to the substrate is guided into the opening 168 and received there. A further connection step takes place in that the conductor body 18 is welded to the inner wall of the opening 168 by means of welding, for example laser welding.

Reference symbols

10A, 10B

Half bridge

12

Semiconductor switching element

122

Drain contact (current contact)

124

Source contact (power contact)

126

Gate contact

14

upper metallization

142

opening

144

first page

16

Circuit board

161

bottom

162, 164, 166

Metallization

168

opening

18

Conductor body

Claims (10)

Half-bridge (10A, 10B) for an inverter for supplying current to an electric drive in an electric vehicle and/or a hybrid vehicle, comprising: - a plurality of semiconductor switching elements (12) which form a high side and a low side connected in series with the high side, wherein during operation of the half-bridge a higher electrical potential is present at the high side and a lower electrical potential is present at the low side, - a substrate, on the first side (144) of which the semiconductor switching elements are mounted and on the second side opposite the first side of which a heat sink of the inverter can be connected, wherein the inverter has a circuit board (16) on which a plurality of electronic components for switching the semiconductor switching elements (12) are connected to them via a plurality of power and/or signal lines, wherein a conductor body (18) is fastened between the circuit board (16) and the substrate, so that the conductor body (18) is received by the circuit board (16) in a form-fitting, force-fitting and/or material-fitting manner in order to form an electrical line between a power contact (124) of the semiconductor switching elements (12) and a metallization (14) on the first side (144) of the substrate, wherein the substrate has a second opening (142) in which the conductor body (18) is received at its substrate-side end in a constructed state of the half-bridge (10A). Half bridge (10A, 10B) after Claim 1 , wherein a metallization (164) is provided on an underside (161) of the circuit board (16) facing the semiconductor switching elements (12), which metallization connects the current contact (124) of the semiconductor switching elements (12) and the conductor body (18) in an electrically conductive manner. Half bridge (10A, 10B) after Claim 1 or 2 , wherein the circuit board (16) has a first opening (168) in which the conductor body (18) is received at its circuit board-side end in a constructed state of the half-bridge (10A, 10B). Half bridge (10A, 10B)) to Claim 3 , wherein the first opening (168) is a through-opening through which the conductor body (18) is passed in a direction pointing towards the substrate. Half bridge (10A, 10B) after Claim 3 or 4 , wherein the conductor body (18) is connected to an inner wall of the first opening (168) by means of frictional forces and/or a welding process, for example a laser welding process. Half bridge (10B) after one of the Claims 1 until 5 , wherein the conductor body (18) is attached to the substrate at its substrate-side end by means of a soldering process and/or a welding process. Power module for an inverter for supplying current to an electric drive in an electric vehicle and/or a hybrid vehicle, comprising a plurality of half bridges (10A, 10B) according to one of the Claims 1 until 6 , each of which corresponds to a phase current of a multiphase alternating current generated by the inverter. Inverter for supplying current to an electric drive in an electric vehicle and/or a hybrid vehicle, comprising a power module and a circuit board (16) on which a plurality of electronic components for switching the semiconductor switching elements (12) of the half-bridges (10A, 10B) are connected to them via a plurality of power and/or signal lines. Method for producing an inverter, comprising: - providing a plurality of semiconductor switching elements (12) which form a high side and a low side connected in series with the high side, wherein, during operation of the half-bridge, a higher electrical potential is present at the high side and a lower electrical potential is present at the low side, - attaching the semiconductor switching elements (12) to a first side of a substrate, on the second side of which, opposite the first side (144), a heat sink of the inverter can be connected, - fastening a conductor body (18) between a circuit board (16) of the inverter and the substrate, so that the conductor body (18) is received by the circuit board (16) in a form-fitting, force-fitting and/or material-fitting manner in order to provide an electrical line between a current contact (124) of the semiconductor switching elements (12) and a metallization (14) on the first side (144) of the substrate, wherein a plurality of electronic components for switching the semiconductor switching elements (12) are arranged on the circuit board (16). are connected to these via a plurality of power and/or signal lines, - providing a first opening (168) in the circuit board (16), - connecting the semiconductor switching elements (12) mounted on the substrate to the underside of the circuit board (16) so that the power contact (124) of the semiconductor switching elements (12) is electrically conductively connected to an underside metallization (164) of the circuit board (16), - attaching the conductor body (18) to the circuit board (16) so that the conductor body (18) is received in the first opening (168) in a built-up state of the inverter and electrically conductively connects the underside metallization (164) of the circuit board (16) to the metallization (14) on the first side (14) of the substrate, - providing a second opening (142) in the substrate before the semiconductor switching elements (12) mounted on the substrate are connected to the underside of the circuit board (16), - passing the conductor body (18) through the first Opening (168), which is designed as a through opening, and into the second opening (142). Procedure according to Claim 9 , further comprising: - fastening the conductor body (18) on the first side (144) of the substrate before the semiconductor switching elements (12) attached to the substrate are connected to the underside of the circuit board (16), - connecting the conductor body (18) to an inner wall of the first opening (168) by means of a welding process, in particular a laser welding process.

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